Add intermissions

Description

We need to add intermissions between question subsets (when the number on the car changes). The main function of these is to give students a pause and to make it evident that that the number on the car is changing.

One way to do this would be to have a banner with the new target on it (like in the Hurix implementation). But the car should slow way down, and the number can float from the banner to the car, and then the car speeds up and you're off and running.

Intermissions added. Car and timer pauses during intermission, new values appears scaled up at the top of the screen, flashes, scales down and moves behind the car. Old value fades out during this time. After intermission, car resumes previous speed. Turbo boost is canceled when hitting an intermission, just like a question.